Aircraft wing tip fuel tank installation



July 11, 1950 D. L. M F 2,514,888

AIRCRAFT WING TIP FUEL TANK INSTALLATION Filed Jan. 31, 1947- 4 Sheets-Sheet 1 INVENTOR.

Dv L. Mc Farland ATTORNEY July 11, 1950 Filed Jan. 31, 1947 D. L. M FARLAND AIRCRAFT WING TIP FUEL TANK INSTALLATION Sheets-Sheet 2 INVENTOR.

Mc Fqrland ATTORNEY July 11, 1950 D. L. M FARLAND AIRCRAFT WING TIP FUEL TANK INSTALLATION 4 Sheets-Sheet 3 Filed Jan :51, 1947 INVENTOR. D-L. Mc Farland BY 7 /3. Wm

ATTORNEY July 11; 1950 D. M FARLAND AIRCRAFT WING TIP FUEL TANK INSTALLATION 4 Sheets-Sheet 4 Filed Jan. 31, 1947 d n a E d V a W F C M L D BY 4 7. 6. WW

ATTORNEY Pate'ntecl July 11, 1950 AIRCRAFT-"WING TIP FUEL TANK INSTALLATION Donald? McFarland, Milford; Conn.,. assig-nor: to Unitedi Aircraft: Gorporation,,. East Hartford,-,

Qonm, a; corporation of Delaware;

Applicatton'lanuarx 31, 1947, Serial No'. 725,439

This invention' relates to aircraft; and particu'e l'arly to airplanes adapted to carry; disposablewing tipunit's;

Conventional cambered wing tips haveeshapes" installation; of; drop: tanks more complicated; add

considerable weight: and? decrease" the: performance of the; airplane.

Itsis: an; object: of this inventionto; provide. an improved wing tip constructiona tor-r supporting-2 drop tanks: and: the; like;

A further object of this invention is toproduce? an; improvedwing;tipzconstruction whichssforms a section between: the: tanlc anda the: outer: wing; panel that issmooth= and; aerodynamicallp clean. andl which actually: increasesl the; efieetiverarew of; the; wing, thus reducing 7 wing loadingand ins-V creasingthe efliciency.- of; the airplanes.

A further object of the invention is to providea Wing: tip and; droppable: tankv constructiong in which the intersectioni between the: wing; andgthe tank; is; a continuous. linerthat; oircumscnibea the: outer wing, panel. extremity and eliminates. the: necessity for filletsbetween: thawing and. the. tank. at their; intersectiom,

A further object ofv the invention; is the] provision. of: a. wing tiprand, drop. tanks construction in: which the dropCtanksYat-the wing tip extremities. of. the twoi wings are. interchangeable A still-further object of the inventiomis-genorally. to, improve the. constructiomand periorm: ance: of, airplanes. equip ed. with, disposable. wing; tipQunits.

These. and other objects. and advantages of. the invention will be apparent or will be. pointed" outin connectionwith the following detailed description' of the accompanying; drawings-- which Glaims. (Cl. .244- 135?) Fig; 7 is a front view ofa, wingtip with. a. fuel'l tank: secured thereto:

Fig; 8'- is a View looking outboard: of the right hand wing tip showing-thetanlr carried attach:-- i'ng mechanism;-

Fig; 9 is1a-view: lookinginboardof the:leit:-hand: wing tip showing the wing-carried attaching" mechanism; and

Fig; 10 -i's a perspectiveview of the wing tip' and; the outer'portion of the wing: panel; similar to- Fig 5; but with the centrali portion. broken away; to show chord lines:

Referring. to Fig: 1, an" airplane generallywinidioated: at; liflf has a fuselage i=2; oppositely ex.-- tended wings. l4: and i6; horizontal andeverticaltail surfaces i'8t and 2BandaaforwardipilotcompartinentJZZ. The outer panels ofjwings M- and kit end: abruptly in a: chordal section: '24: andare; provided: with trailing edge ailerons: whichterminatezjustshort of thetips of the-outer wing panels. Replaceable wing; tips, one of which} is generally indicated by: the-numeral 25in Fig. 2; are; securedto; the; tips of the outer wing panels byv piano hingesa 28-and 30-; thecooperating sec-- tions of each: of; which are carried by the upper andziower" shell structure of the wing: panel,- and the wing; tip surfaces; respectively. In order toform; at good line. of intersection between the wing. tipwand the-outerwing panel, astrip132-of metal is-iprovidedfwh-ich extends around the wingipanel. tipaandis securedpthereto andto; which the panel carried! strips othinges 28* and: 3t 1 are secured.

Detachable wing: tips: per se are wellknown; Thewingiti'psi 2.6;. however, are of an improved construction which enablesthem to. receive wing tip drop tanks 34. in: an: improved manner by whichzthe section .betweenthe; tanks and'thewing outerr panels: is: smooth: and: aerodynamically cleam.

To; this. end: the" wing tip. 25: is constructedv so thati it: is: symmetrical about a wing tipchord line; which isoutboard of'and parallel with thezchordline; 38mins the: outer panel section 24. mchordis an: arbitrary: datum linefrom whichthe; ordinates; and angles: ofan airfoil are: measurerli In; accordance: with generally acceptedpractioe; and' in, this; instance, chord line: 38. is the straight linebetweenthe leadingv and: trail ing zedges'iof the wing; at section- 2 generally parallel to; thezlongitudinah axis; of the airplane and, simii'arly,. chord line. 36: isv the: straight line hetweemthe. leading. and; trailing; edges of the-wing tipi'parallelz to; chord line-38; As showmin Fig. 10; ohord line38 of thewing at section. 24 and, chord line 36 of the wing tip are parallel-and betm lie..-

As shown most clearly in Fig. 1 the drop tanks 34 are provided with a cylindrical mid-section 42 which is at least coextensive with the chordal length of the wing tips 26 and this cylindrical section is provided with an inboard well 44 in position to receive a little more than 180 of the throughout For the purpose of making the tanks interchangeable, and since the ends of pins I are identical with the ends of latch plungers I0, the pins I00 may also be seated in apertures 96 and the latch plungers I0 may also be receivable in the apertures 08. Thus a tank 34 which is on one wing tip where thewing tip carried latch plungers ,10, are' received in the tank apertures 96 and the pins I00, which are seated in tank apertures 98, have their projecting tapered ends received in wing tip apertures 82, can be rotated bodily over the'top of the airplane to position it on the other wing tip in which case the pins I00 would-be seatedin tank apertures 96, which would then :be'lowermost; and would enter the lower apertures 82' of the wing tip and the wing tip periphery of the cylindrical wing tip 26. It will be noted that said intersection forms a continuous line 46, generally elliptical in shape, that circumscribes and accurately conforms to the entire outer panel extremity and thus eliminates the need for fillets between the tank and the wing surfaces which were formerly required when a drop'tank was installed on a non-symmetrical wing tip.

Cooperating locking mechanisms generally indicated at 43 and 50 respectively are carried by the wing tip 26 and the tank 34 respectively of eachwing. As shown most clearly in Fig. 9, locking mechanism 48 includes a casting 52 which is secured by bolts passing through lugs 54 at the opposite ends of the casting to the fore and aft wing beams (not shown). The casting 52 includes integral pairs of webs 56 and 58 adjacent its ends having bridging arcuate surfaces 62 above the median'plane of the wing and similar arcuate surfaces 64 below said plane, these surfacesbeing flush with and projecting through apertures 66 and 68 in the wing tip shell. Surfaces 62 have apertures 69 therein through which latch plungers I0 are projectable by toggle mechanism including a link I2 and arms I4 fixed on a latch operating shaft I6. The latch plungers I0, which have cylindrical, tapered ends, are a part of bellcrank shaped members I0 pivoted on bolts 80 between the spaced webs 56 and 58 so that when the toggle comprising links I2 and arms I4 are in the straightened position shown in Fig. 9, the cylindrical plungers I0 are projected beyond the arcuate surfaces 62, and hence beyond the cylindrical surface of the wing tip 26. The surfaces 64 on the lower surface of the wing tip have apertures 02 therein the purpose of which will hereinafter be explained.

The locking mechanism in the wells of the right and left hand drop tanks are identical and while a right hand tank is shown in Fig. 8, its locking mechanism will be described as applying to a left hand tank matching the locking mechanism in the left hand wing tip described above. The looking mechanism 50 in the wells of each of the drop tanks 34 includes a casting 00 which is generally semi-circular in configuration and is provided with upper pads 92 and lower pads 94 provided with apertures 96 and 98 respectively. The upper apertures 96 are adapted to receive the tapered cylindrical latch plungers I0 and the lower apertures 98 are adapted to receive one end of pins I00, the projecting tapered cylindrical ends of which are identical with the ends of latch plungers I0. The projecting ends of pins I00 are refaces of casting 52.

latch plungers I0 would enter tank apertures 96 which would then be uppermost.

The rotation of shaft I6 to break the toggles I4, I2 is under the control of the pilot. To this end pilot operated control mechanism (not shown) is provided in the cockpit 22 which is connected by cables I02 to a sector-wheel I04, located between webs I 05 of casting 52, which wheel is operatively connected with an arm I06 splined to the shaft I6.

When it is desiredlto release the tank, the pilot operates his controls to rotate the shaft I6 and break the toggle .14 and I2, thus rocking the bellcranks I8 and withdrawing the latch plungers I0 from the upper apertures, as for example the apertures 96 in Fig. 8.- The tank thus released swings outwardly at the top away from the wing tip until it is clear of the latter, as guided by the pins I00; v

The above described locking and releasing mechanism is described more in detail and is claimed in a copending application, Serial No. 725,902, filed February 1,1947, now matured into Pat. No. 2,505,604, and reference is made thereto for a more detailed understanding of these mechanisms. I

'It will be evident that as a result of this invention an improved wing tip construction has been provided for supporting disposable units on tips of an airplane by which the junction between the wing and the unit is aerodynamically clean without the use of fillets? It will also be evident that a construction has been provided by which left and right-hand drop tanks are avoided and any tank can be installed on either wing. Also as a result of this invention a drop tank construction has been provided having a minimum of weight and drag and by which the lift of the wing is actually increased by the presence of the tank.

While only oneembodiment of the invention has been shown and'described herein it will be evidentthat'various changes in the construction and the arrangement of the parts may be resorted to without departing from the scope of the invention. For example, the invention is not limited to drop fuel tanks but is equally applicable to any other disposable unit which may be attached to a wing tip. I .1

What'it is desired to secure by Letters. Patent is:

1. In an airplane, a wing having upper and lower surfaces and having a tip which is enlarged about a fore-"and-aft axis relative to the thickness of the adjacent wing section, said tip being formed-by rotating a lateral extension of the upper wing surface, taken at its extremity, abouta line in said tip parallel to a chord line at the extremity of said wing until the surface of revolution generated by said rotation intersects the lower wing surface.

2. In an airplane, a wing having upper and lower surfaces and having an outer panel terminating in an outer panel-tip section and a wing tip enlarged about a fore-and-aft axis relative to the thickness of the adjacent wing section comprising a surface of revolution formed by rotating a lateral extension of the upper surface line of said outer panel at said tip section about a chord line of said tip section until it intersects the lower surface of said panel.

3. In an airplane, a wing having upper and lower surfaces and having an outer wing panel terminating in a wing chord section and a wing tip forming an extension of said section, said wing tip terminating in a'surface of revolution formed by rotating a lateral extension of the upper surface line of said wing at said section about a chord line of said wing tip located outboard of said section until the surface of revolution enerated intersects the lower surface of said panel, said lateral extension of the upper surface line of said wing at said section being extended laterally to a vertical plane through said chord line of said wing tip.

4. In an airplane, a wing having upper and lower surfaces and having an outer wing panel terminating in a wing chord section and a wing tip forming an extension of said section, said wing tip terminating in a surface of revolution formed by rotating a lateral'extension of the upper surface line of said wing at said section about a fore and aft axis of said wing tip parallel to but outboard of a chord line of said wing at said section until it intersects the lower surface of said wing panel, a drop tank having a well in its side to receive said wing tip, and cooperating locking means carried by said wing and tank for releasably securing saidtank to said wing tip, said lateral extension of the upper surface line of said wing at said section being extended laterally to a vertical plane through said fore and aft wing tip axis. v

5. In an airplane, a wing having upper and lower surfaces and a wing tip enlarged in spanwise section relative to its adjacent wing section and forming an extension of said surfaces, said wing tip having a generally circular spanwise cross section at any point along a fore-and-aft chord line of said wing tip and having its upper most surface at any point along the length of said wing tip in the same horizontal plane as the adjacent upper surface of said wing, a drop tank having a cylindrical mid-section provided with a Well in its inboard side into which said wing tip projects, and cooperating locking means carried by said wing and tank for releasably securing said tank to said wing tip.

DONALD L. MCFARLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,074,201 Bechereau Mar. 16, 1937 2,421,699 Johnson June 3, 1947 2,485,218 Shaw Oct. 18, 1949 FOREIGN PATENTS Number Country Date 850,918 France Sept. 25, 1939 

